between old and new reference frames (position Beginning in 1988 the Federal Office of Topography and height) (swisstopo) has conceived a new national geodetic -Linking the Swiss Positioning Service swipos to reference system CHTRS95 which should replace the those of the neighboring countries (e.g. SAPOS) existing frames LV03 (position) and LN02 (height) -Practical application of GPS humidity measure-with its new reference frames CHTRF95 (global) and ments to meteorology LV95 (local). CHTRS95, which is closely related by a

geometric transformation to ETRS89, also consists of 2Fundamental Station Zimmerwald a new height system, a geoid model on the cm level The fundamental station Zimmerwald is jointly oper-and a kinematic model. ated by the Astronomical Institute of the University of After 15 years most elements of the new system have Berne (AIUB) and the Swiss Federal Office of been realized and most of the data is available to the Topography (swisstopo). user. The fundamental station Zimmerwald together

with 5 EUREF stations links the national networks to 2.1SLR observations

the European and worldwide reference frames. Since 1997, when the first SLR observations were Various geodetic measuring techniques such as SLR, performed with the new SLR system in Zimmerwald, GPS and gravimetry are already collocated at a continuously increasing number of observed passes Zimmerwald. As a contribution to the ECGN initiative, could be submitted to the International Laser Ranging the number of measuring techniques is presently Service (ILRS). being increased.

Although there was an almost two-month shutdown The Automated GPS Network (AGNES) with 29 of the station due to maintenance (re-coating of the permanently operating GPS stations is used for primary mirror), Zimmerwald ranked # 9 out of about various applications such as real-time positioning and 40 stations regarding the total number of collected GPS meteo. It is optimally integrated into the EUREF passes, and # 5 in the rating with respect to the permanent network. The national GPS network LV95 number of Lageos normal points. From March 16 to has been densified and includes 206 well-22, 2003, Zimmerwald collected the largest number of monumented control points. A large effort has been passes for that week worldwide. undertaken to establish a new height reference frame

Thanks to the possibility of automated and unat-LHN95 which, together with the new geoid, is

tended operation or remote control during limited compatible with the 3D frame of LV95.

times (typically a few hours per day), a nearly 24-hour Presently geodetic work is focused on the following tracking coverage can be realized with only two shifts tasks: per day. -Connecting geodetic networks (AGNES, LV95,

Zimmerwald was the first ILRS station to submit dual-LHN95 etc.) with the objective of making them

color range observations on a regular basis between compatible (GPS–leveling)

mid-August and December 2002. -Completing the combined kinematic adjustment of

receiver) Parallel to the software updates, the server archi-The Trimble receiver runs with the GPS Base Station tecture was enhanced. The VRS computation was Software and provides daily files to the IGS data separated from the data communication and the data centers. Furthermore, hourly files are generated and storage on the Web server. In addition, a new distributed with a time delay of a few minutes, and software tool allowing the VRS computation for post-are used for near real-time applications by the IGS and processing applications was installed on the AGNES other institutions. The delivery rate of the daily Web server. The new configuration provides a observation files was very high during the last three maximum flexibility for data communication (e.g. years: 99% for 2000, and nearly 100% for 2001 and data exchange over the Internet, see below). 2002. In addition, the Trimble receiver provides

The real-time service swipos-GIS/GEO and the cor-epoch-wise GPS data in real-time to the central

AGNES server, which is one of the currently 29 responding SAPOS service in Baden-Württemberg

which will be replaced by an Internet connection as In addition to the main GPS receiver, two combined soon as possible. The data of 9 stations are exchanged GPS/GLONASS receivers are installed at Zimmerwald, on a real-time basis, allowing an improvement of the both providing data for the IGLOS-PP. This quality of VRS processing in the region along the International GPS Service Pilot Project is a follow-up border between Germany and Switzerland. project of the former IGEX-98 campaign and Connections to SAPOS in Bavaria (Germany) and to maintains a global station network and provides Austria are planned and will be realized within the precise orbits for the GLONASS satellites. next year.

2.3Contribution to ECGN The developments of EUREF-IP were followed closely.

First tests were performed in August 2002 and Switzerland contributes to the ECGN project with showed good results even for RTK applications over various observations in Zimmerwald [Brockmann et Internet. Swisstopo would therefore like to become al., 2003]. an "Internet Broadcaster" within EUREF-IP for DGPS

correction data. The installation of the corresponding 3Permanent GPS network AGNES and server infrastructure is planned for the end of 2003. positioning service

The Automated GPS Network of Switzerland (AGNES) 4Analysis of permanent GPS networks reached its final configuration of 29 stations by the The permanent GPS networks analyzed at swisstopo end of 2001. During 2002 the last refinements of the are shown in Tab. 4-1. station installations were done, including an improved

lightning protection unit and a remote-accessible NetworkStationsAnalysis interval; power switch for the station computers. In addition, Delaylocal ties and the connection to the old national first EUREF daily; after 21 order network LV03 were measured at 23 stations in 20 (1 AGNES)subnetdaysorder to contribute to the determination of the

transformation parameters between the old (LV03) AGNES + daily; after 21 65 (29 AGNES)and the new reference frame (LV95). EUREFdayssubnetThe overall performance of AGNES was excellent, and

AGNES + the availability of the RINEX data files on the Web hourly; after 0.5 EUREF63 (29 AGNES)server was 99.1% (mean value over all stations). At 20 hourssubnetstations the station outages were below the indicator

of 3 days/year, at 9 stations this value could not be Tab. 4-1: Routine GPS data analysis at swisstopo attained. These "critical stations" were identified, and

The data of the AGNES sites have been monitored organizational and technical actions were taken in

since the end of 1998 on a daily basis. In addition to order to improve the availability of the data.

the 29 AGNES sites, 40 EUREF permanent sites are For the real-time positioning service swipos-GIS/GEO, processed with the Bernese GPS Software Version 4.2 a new version of the Virtual Reference Station (VRS) [Hugentobler et al., 2001] using the final IGS orbit software was installed, which performed better with products with a time delay of 3 weeks. This respect to stability, initialization times and accuracy. monitoring allows the detection of possible site In addition, the new software version allows the movements. An updated multi-year solution, where storage of real-time estimates of the troposphere. the site coordinates and velocities are solved for, is Comparisons of these "real-time" tropospheric automatically generated after having processed an parameters with those of our geodetic post-additional week of data. The results are e.g. estimated

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velocity and repeatability plots. As an example, the 5National reference frame LV95 and

horizontal velocities relative to Zimmerwald are its relation to the old networks shown in Fig. 4-1.

5.1The national reference frame LV95

The densification of the GPS network LV95 has been

completed on the national level. There are a total of

206 well-monumented control stations serving as the

basis for the reference frame. In order to ensure the

transition between the old and the new reference

frame, transformation programs were developed, one

each for height and position. These control points

together with the AGNES stations serve as a reliable

basis for the determination of the transformation

check points.

5.2Transformation LV03 ; LV95

As in many other countries, the transformation be-

Fig. 4-1: Horizontal site velocities in ITRF00 (rela-tween the old reference frame (LV03), determined tive to Zimmerwald. The time span of the mainly by triangulation, and the new GPS reference sites with the longest “history” is summer frame (LV95) still has to be realized. Due to the dis-1998 till May 2004). tortions of the triangulation network in the order of

more than 1.5 m (see Fig. 5-1), a simple modeling of Since 1999 swisstopo has been active in the European the differences by means of a 4-parameter similarity project COST-716 (exploitation of ground-based GPS transformation does not give adequate results. A for climate and numerical weather prediction possible solution would be to divide the country into application). After a successful benchmarking [van der sub-regions and to use individual transformation Marel et al., 2001], swisstopo has been contributing parameters for each sub-region. But this would result zenith total delay estimates in near real-time (NRT-in ambiguous coordinates along the boundaries. ZTD) since December 2001. 95-98% of the solutions Another possibility that was chosen by several arrive at the data archive of the UK met office within 1 countries was to model the differences by polyno-hour and 45 minutes. mials of a certain degree. This method causes the MeteoSwiss used the NRT-ZTD estimates in a test problem of reversibility of the transformation and can study for numerical weather prediction. The numer-lead to unrealistic results in regions without known ical forecast models were computed for the different common points. test periods (summer, autumn, winter) in two Switzerland has chosen another method which is different schemes: a run with assimilated GPS-derived called FINELTRA (finite element transformation), ZTD estimates and a run without assimilated ZTDs. A whereby the whole territory is covered with triangles. comparison of the results showed a positive impact of For each of these triangles an affine transformation GPS [Guerova et al., 2002]for summer and a slightly with 6 parameters is defined. This method has the negative impact for winter. A by-product of the hourly following advantages: processing is the monitoring of the site coordinates.

coordinates at the boundaries allow the detection of coordinate changes of the

-the transformation is reversible and works in both order of 2 cm.

directions Swisstopo will also be active in the follow-up Euro--the common points which are used as transfor-pean project TOUGH "Targeting Optimal Use of GPS mation check points in both networks transform Humidity Measurements in Meteorology" (2003-2005). exactly to the coordinates of the other network

Since January 2003, ZTD values can also be extracted Up to now the mesh of triangles has been defined on from the real-time positioning software GPSNet 2.0 stndthe level of the 1 and 2 order triangulation points with accumulation intervals of 1 minute with a (Fig. 5-2) which allows a transformation in the order negligible time delay. of about 5 to 20 cm, depending on the region and the

quality of the old triangulation. Presently the cantonal The results of the different analyses are available on

surveying authorities are working on further http://www.swisstopo.ch/en/geo/pnac.htm.

densifying the triangles.

Since FINELTRA is a rather special solution which

cannot be implemented easily in GPS receivers, an

approximation of this method had to be developed,

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where the differences between LV03 and LV95 are real-time. For a 1-km grid maximal differences are calculated in a regular grid of 1-km spacing. This grid usually better than 1 cm compared to the solution of can be stored directly in the GPS receivers and the FINELTRA.

surveyors obtain the still official LV03 coordinates in

Fig. 5-1 Differences LV95 minus LV03

the differences into one part that is a function of only

the horizontal position and into a second part that is a

function of the elevation as well. The first part (Fig.

5-3) is identical to the differences between LN02 and

normal heights, and reaches amounts between -20

and +10 cm. This part includes the distortions of LN02,

the influence of vertical movements and a part of the

influence of the gravity field. It shows practically no

correlation with height.

The second part of the differences, which is identical

to the difference between normal heights and

orthometric heights, works like a local scale factor. It

reaches amounts between -40 and +220 ppm. The stndFig. 5-2 Triangles defined by 1 and 2 order Bouguer anomalies are a very good approximation for

triangulation points this scale factor.

Therefore, the total of the differences are modeled by 5.3Transformation LN02 ; LHN95 the function A similar problem as the one for the position is the

transformation of heights between the old leveling g(x,y)ΔBougH=H+f(x,y)Hnetwork LN02, which was adjusted without taking LHN95LN02ginto account the influence of the gravity field, and the

new orthometric height system LHN95. Due to the The transformation calls for one grid that represents special structures of leveling networks, an approach the differences between LN02 and normal heights with triangles, as it was used for position, is not f(x,y), and another grid of the Bouguer anomalies. recommendable. In addition, the differences between Near the leveling lines and in flatter areas, the LN02 and LHN95 show a strong correlation with the accuracy of the transformation is in the order of height. Therefore, an approach was chosen that splits

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?2 mm. In mountainous regions the accuracy is de-Fig. 5-4 shows the total of the differences between creased and can reach amounts of up to 2 cm. LN02 and LHN95, which are between -20 and +60 cm.

6.2National control points 6Maintenance of networks in This maintenance concept includes the following Switzerland networks: The organization and the revision cycle of the various -the permanent stations of the Automated GPS networks are defined in the internal report 02-01 Network of Switzerland, AGNES (including the "Landesvermessung der Schweiz, Unterhaltskonzept fundamental station Zimmerwald) der geodätischen Netze" [Santschi et al., 2002]. The -stations of the GPS network LV95 revision work, quality standards, data management, -transformation fiducial points for the conversion of documentation and archiving are defined for the the national triangulation network LV03 ; national various categories. All stations of the European GPS control network LV95 (first order points) networks are integrated in these categories and thus -control points of the old LV03 (first order points) their maintenance is ensured.-height control points (benchmarks) of the national

height network LHN95 (first order points) 6.1EUREF stations -test networks of the national survey This maintenance concept includes the following

1) Maintenance will be discontinued when LV95 is introduced as the reference frame for all surveying applications in

Switzerland

Tab. 6-1 Maintenance concept of the Swiss control points

In the scope of the transition from the old triangula-7Current projects tion network LV03 to the new GPS control network

LV95, it is very important to maintain and keep up the 7.1Control point data service data of the control points. In order to achieve this goal, The schedule of the initial project "Datashop Geo-close collaboration is required between the Geodesy desy" was revised and renamed "Control point data Division, the Federal Directorate for Cadastral service" in June 2001. The focus of this project is no Surveying and the cantons. Currently a Java user longer in just preparing the data of the control points interface is being programmed and the data from for use on the Internet, but in establishing and swisstopo and the cantons are being imported. updating a central database of the control points together with the surveying authorities of the cantons, whereby the data will be made available to customers via the so-called "Central Point of Delivery".

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-finishing the scans for the site documentation 7.2GIS for the national border

-developing the new database in the scope of the The responsibility of the technical administration and project "Control point data service" (see chap. 7.1) the maintenance of the national border network lie with the Geodesy Division. For some time already, the The introduction of LHN95 as the official vertical ref-main focus has been on drafting a new maintenance erence frame for cadastral surveying was rejected by and documentation concept on the one hand, and on the surveying authorities of the cantons. Therefore, coordinating this information with the official the valid height reference frame for official cadastral cadastral surveying data on the other hand. Therefore, surveying is still the "old" LN02. However, LHN95 will in addition to the daily business, the efforts were remain indispensable for applications in national concentrated on this concept, which resulted in the surveying, scientific research, for the integration of new project "National Border". European height systems, and for large engineering The project consists of the following tasks: projects such as the new Alpine railway tunnels

(AlpTransit). As a consequence, increased significance -securing and maintaining the points of the national will be placed on the software for the transformation border together with the neighboring countries between LN02 and LHN95. -modernizing the data management and docu-

mentation 7.4Swiss 4D: Establishing a kinematic -making the coordinates available in the European

model for Switzerland reference frame ETRF89 as well as in the reference

frames of the neighboring countries Based on the data of the Swiss permanent GPS -preparing the data and their integration in the GIS of network AGNES and repeated measurements, the official cadastral survey and in the topographic swisstopo is developing a kinematic model in col-database laboration with the Geodesy and Geodynamics Lab of

the Swiss Federal Institute of Technology in Zürich, The data management is to be part of a GIS. The which will take into account recent tectonic same instrument should also be used for the ad-movements (see Fig. 7-1). ministration of the boundaries between cantons,

districts and municipalities. In addition, the data The determination of a local–regional kinematic model should be revised and made available in the model for Switzerland (CHKM95) is an essential geographic data standard INTERLIS in order to component of the new definition of the Swiss geo-guarantee a uniform data transfer. This conversion detic reference system CHTRS95. CHKM95 describes should be realized by the end of 2007. regional movements in Switzerland relative to the

European reference system ETRS89 as well as local 7.3New national height system LHN95 movements in the geodetic networks LV95 and The activities in 2002 were mainly focused on the LHN95 in all three dimensions.

following subjects: Last but not least, the deformation of space and time -integrating the new observations 2001/02 of the 1st will be analysed so that tectonic interpretations are order leveling network and the connections to the possible. Continuous spatial velocity or strain rate AGNES and LV95 stations fields are suited for the description of the deformation -documenting the network concept LHN95; processes. Also, seismic and geological information is observation schedule 2004-2008 of interest. -collaboration in the CHGeo2003 campaign [Brockmann et al., 2003]